NZ201317A

NZ201317A - Control system for blank presser

Info

Publication number: NZ201317A
Application number: NZ201317A
Authority: NZ
Inventors: M Tokuno; T Sawada; Y Mori
Original assignee: Rengo Co Ltd
Priority date: 1981-07-20
Filing date: 1982-07-19
Publication date: 1984-10-19
Also published as: NL189854C; US4577746A; IT8222368A0; DE3227092C2; FR2509703A1; GB2105875B; ATA279382A; AT385970B; NL8202871A; NL189854B; GB2105875A; SE8204394D0; IT1190915B; CH649398A5; SE456819B; SE8204394L; DE3227092A1; CA1180427A; AU549918B2; FR2509703B1

Description

d 1 3 f 7 OCT 198* N-. Z. No.

NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION "CONTROL SYSTEM FOR BLANK PRESSBR." We, RENGO CO.,LTD., a Japanese company of 1-186, Ohiraki 4- chome, Fukushima-ku, Osaka-shi, Osaka, JAPAN do hereby declare the invention, for which v?e pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- (Followed by IA.) Z 9 11 5 II 7 CONTROL SYSTEM FOR BLANK PRESSER The present invention relates to a control system for a blank presser used to timely and lightly touch down blanks fed from a conveyor, thereby preventing them from scattering or jamming up. The control system is adapted to adjust the movement of the blank presser automatically in response to any change in the blank feed speed and the blank length.

In the production line of corrugated fiberboard,. a web of corrugated fiberboard is cut into blanks of a predetermined length by a rotary cutter, said blanks being fed by a first conveyor running at a slightly higher speed than the web speed and then further fed shingled on a second conveyor running at a slightly lower speed than the first conveyor. At the supply end of the second conveyor, there is usually provided a blank presser. The first conveyor serves to prevent the jamming between the rear end of the last blank just cut and the "front end of the web and/or the cutting blade of the rotary cutter. The second conveyor serves to bring the blanks fed one after another into a shingled state. Also, the blank presser serves to press or hold down the blanks fed at a high speed, thereby preventing them from- scattering or jamming up.

The best timing for the blank presser to hold the blank - lft- 2013 17 is at the instant the blank leaves the first conveyor or just before or just after that. If the timing were too late, the blanks would scatter and jam up, causing trouble. If the timing were too early so that the blank is held by the presser before it leaves the first conveyor, the blank would be rubbed by the first conveyor, interfere with the next blank or be bent between the first conveyor and the second one.

Also, the period at which the blank presser touches the blanks has to be changed each time the blank length or the blank feed speed is changed. Further, the length of the first conveyor has to be taken into consideration for optimum timing. Conventionally, the movement of the blank presser had to be watched and adjusted by hand each time the blank length or the blank speed changes.

An object of the present invention is to provide a control system for a blank presser which eliminates the need of watching and manual adjustment of -the blank presser even in the presence of any change in the blank length or blank speed.

In accordance with the present invention, a control system for controlling a blank presser used to touch or hold down each of blanks fed one after another from a conveyor, said control system comprising setting a value (L) proportional to the length of the blanks fed from said conveyor and a value (J?) proportional to the distance 2013 17 by which said blank presser moves in one cycle of its operation, generating a signal ( ) proportional to the speed at which said blanks are fed and a signal (^g) proportional to the speed of said blank presser, performing computation expressed by Jl/L x ^ combining an error voltage proportional to the result of computation with a reference voltage proportional to said signal (9^ p) multiplied by j£/L, and controlling a drive for said blank presser by use of the combined voltage so that the blanks will be held down by said blank presser at a correct timing.

Other features and advantages of the present invention will become apparent from the following description taken with reference to the accompanying drawings, in which: Fig. 1 is a view showing the conventional blank presser in use; Fig. 2 is a similar view showing a blank presser used in the present invention; Fig. 3 is a block diagram of a control system according to the present invention; and Fig. 4 is a block diagram of an example of the first counter and the divider.

-Referring first to Fig. 2 showing a blank presser used in the present invention, a web 1 of corrugated fiberboard is fed by a pair of feed-rolls 2 to a rotary cutter 3 where it is cut into blanks B of a predetermined length. The blanks are fed on a sandwitch belt conveyor 4 to a belt conveyor 5 which feeds the blanks to the next station. The sandwitch belt conveyor has at least one pair of belts between which each blank is clamped to be fed. The speed of the sandwitch belt conveyor 4 is set to be equal to or slightly higher than the speed of the web 1 to prevent trouble due to interference between the tip of the web 1 and the rear end of the last blank B. Also, the speed of the belt conveyor 5 is set to be lower than both that of the conveyor 4 and the web speed and the supply end of the belt conveyor 5 is below the discharge end of the conveyor 4 so that the blanks will be shingled on the belt of the conveyor 5 for feeding to the next station. In order to prevent the blanks (fed at a considerably high speed) from jamming up, a blank presser brush 6 is provided at the supply end of the conveyor 5 so as to touch or hold down each of the blanks about just when the blank has left the sandwitch belt conveyor 4.

With the conventional blank presser, .the brush 6 was mounted to be movable back and forth as shown in Fig. 1 by arrow. Conventionally, the position of the blank presser had to be manually adjusted back and forth according to the length of the blanks and the blank feed speed.

Referring again to Fig. 2, a blank presser generally designated by numeral 9 comprises a' presser brush 6 fixedly mounted on an arm 10 through a mounting bar 11, said arm being coupled through a rod 12 to a crank disc 13. By this r. n i 3 n 7 arrangement, the rotation of the crank disc is converted to a rocking motion of the presser brush 6. The blank presser 9 is disposed at such a position that the brush 6 can hold down all the blanks at a fixed position some distance away from their rear end even if the length of the blanks is minimum. The brush is adapted to touch each of the blanks at its fixed position while rocking in a vertical plane.

\ The sandwitch belt conveyor 4 is driven by a first driving motor 7 to which is connected a first pulse generator 8 for generating pulses, the number of which is proportional to the revolutions of the motor 7. The crank disc 13 is driven by a second driving motor 14 to which are connected a tachometer generator 15 giving a signal proportional to the speed of the motor 14 and a second pulse generator 16 for generating pulses, the number of which is proportional to the revolutions of the motor 14.

In order to detect that each rocking 'motion of the brush 6 has completed, a marker 17 is fixedly mounted on the crank disc 13 and a detector 18 is provided near the crank disc to detect the marker, giving a detection signal S. The detector 18 is adapted to give the detection signal when the presser brush 6 starts holding down the blank B.

Next, a control circuit for the blank presser embodying the present invention will be described with reference to Fig. 3. 2 013 Firstly, two values L and are set in a first setter 30. The values L and 9. are proportional to the length of the blanks B and the circumference of the crank disc 13, respectively. These values L and Jl are given to a divider 31 which divides the value i by L to obtain a coefficient K (= i/L) .

A multiplier 32 multiplies the coefficient K by a pulse signal from the first pulse generator 8 which is proportional to the length for which the blank has been fed. The signal from the multiplier 32 is put into a first frequency/voltage (F/V) converter 33 which converts "the frequency of the signal to a voltage, • which is used as a reference voltage for the second motor 14.

A first counter 34 starts the counting of the pulse signal (p in response to an external signal A and gives a timing signal T when the count has reached to a value X proportional to the distance between the web cutting point and the discharge end of the sandwitch belt conveyor 4. The external signal A is a signal indicating that the blank has been supplied to the sandwitch bel*t conveyor 4, e.g. a cutting complete signal given at the instant when the rotary cutter 3 has completed the cutting. The first counter 34 and the divider 31 will be described later in more detail.

A position compensation circuit 35 receives a pulse 2 013 17 signal <f? from the second pulse generator 16, the timing signal T and the detection signal S, checks the position of the marker 17 each time the timing signal T is given, and gives a compensation value E proportional to the amount of deviation from the correct position of.:the -crank disc 13. (It should be at such a position that the brush comes to the operative position just when the timing signal T is given.) The compensation value is set to be negative when the marker 17 is leading against the correct position and be positive when it is lagging.

In the position compensation circuit 35, a second counter 36- for counting the pulse signal from the second pulse generator 16 is reset and restarts the counting each time the detector 18 senses the marker 17 and gives a detection signal S. The count N in the second counter 36 is stored in the memory circuit 37 in response to the timing signal T. The value X, which is the same as the one set in the first setter 30, is set in a second setter 38 and given to a comparator 39, which compares the count N from the memory circuit 37 with the value L/2 and gives a value E (E=-N when N<^X/2 and E=_^-N when N=j^/2.) The comparison of N with Ji/2 is done to check whether the marker 17 is at the correct position or is lagging or leading when the timing signal T is given. * The count N may be compared with a value X/3 or any other suitable value.

Because the control does not have to be so accurate, the position compensation circuit 35 may be adapted so that its output will be zero if the absolute value of the compensation value E is below a predetermined value.

A third counter 4 0 counts up the signal from the multiplier 32 and counts down the pulse signal from the second pulse generator 16. It also reads the compensation value E from the position compensation circuit 35 in response to the timing signal T from the first counter 34 and gives the result of computation, M=K(p - (p+ to a digital/analog converter 41 which converts the value M to an analog error voltage Vc. The error voltage Vc and the reference voltage Va are given to an operational amplifier 4 2 which combines them and gives a speed reference voltage Vo (=VA + Vc) for the second motor 14.

A second F/V converter 4 3 converts the pulse signal from the second pulse generator 16 to a voltage Vg proportional to its frequency. A speed command unit 4 4 compares the voltage VD fed back with the speed reference voltage Vo to check to see if the second motor 14 for the blank presser is operating at a speed corresponding to the reference voltage. If there is any difference therebetween, the speed command unit 44 will add it to, or subtract it from, the reference voltage Vo so that the motor will rotate just at Vo. If the voltage Vo is zero, the speed command unit 44 will stop the motor 14.

The blank presser is controlled so that the crank disc 13 makes one full turn each time one blank is fed from the sandwitch belt conveyor 4.

In short, a computing means 45 including the setter 30, divider 31, multiplier 32, F/V converter 33, counter 34, counter 40, D/A converter 41 and operational amplifier 42 multiplies the pulse signal <p from the first pulse generator 8 by a coefficient K (equal to the circumference A of the crank disc 13 divided by the length L of blanks), counts up the product K <p and counts down the pulse A signal (pB from the second pulse generator, and combines the voltage Vc corresponding to the result of counting, - <fcQ or ~ + E (E is the compensation value from the circuit. 35) with the voltage VA corresponding to the product signal K^/ and gives a voltage V^ + Vc.

Although in this embodiment the product signal is first obtained and then the reference signal V _ is A- obtained therefrom, V may be obtained in any other way, e.g. by converting the pulse signal to a'voltage and multiplying the voltage by the coefficient K.

Referring next to Fig. 4, the first counter 34 comprises a 4-bit ring counter 47 for counting the external signal A, four presettable counters 48a to 48d, and an OR circuit 50. The divider 31 comprises a dividing unit 51, four memories 49a to 49d, and a data selector 52. The counters and the memories with the same suffix make a pair, respectively. The ring counter 47 gives a signal for 2 013 17 selecting one of the counters 48 and its respective memory 49 one after another each time it receives the external signal A. The selected counter starts the counting in response to the signal from the ring counter 4 7 and gives a signal to the OR circuit 50 when its count reaches the preset value X. The OR circuit 50 gives a timing signal T in response to the signal from one of the counters 48. The selected memory 49 registers the output of the dividing unit 51 which reads the values L and J(_ from the setter 30 and performs a division £/L.

The data selector 52 outputs to the multiplier 32 the value memoried in the memory 4 9 associated with that counter 48 from which a signal has been given, from when one counter has given a signal to when the next counter gives a signal. For example, it outputs the value stored in the memory 49a from the instant the counter 48a has given a signal to the instant the counter 4 8b gives a signal.

The number of the counters 48 and the-memories 49 must be the same and may be predetermined according to the length of the blank and that of the sandwitch belt conveyor 4 and thus the value X. The data selector 5.2 may be a memory circuit registering the value registered in the associated memory 49 in response to the signal from one of the counters 48.

The change in the setter 30 from one blank length L (that is the cutting length) to another is done at the same 2013 1 time as the issuance of the external signal A, e.g. in the following manner. The rotary cutter 3 gives a cutting complete signal, that is, the external signal. Iri response to the signal, a new cutting length is written in a setter on the speed controller for the rotary cutter 3. Simultaneously it is set in the setter 30 of the control system according to the present invention.

Although the divider 31 shown in Fig. 4 includes a plurality of memories 49 and a data selector 52, if the web cutting length, that is, the blank length does not change but is fixed, the memories and the data selector may be omitted. In this case, the divider 31 merely registers the value L (blank length) from the setter 30, divides the value JJ. by the value L, and gives the result of division to the multiplier 32.

The divider 31 may be comprised of a plurality of blank length memories paired with the counters 4 8 and a dividing unit. Each time the count of the' ring counter 4 7 changes, the associated blank length memory registers the blank length Ti which will be selected at the same time when the respective counter gives a signal, 'the dividing unit determining the coefficient K (= £/L) and supplying it to the multiplier 32. Thus, the requirement for the divider is that it gives to the multiplier 32 a coefficient determined on basis of the length of the blank next to the blank that has just left the sandwitch belt conveyor 4.

Next, it will be described how the blank presser is controlled if the blank length has changed.

Firstly, let us assume that the web is cut by the rotary cutter into blanks of a length and that L1 is set in the setter 30 and that all the memories 49a to 49d register the coefficient = £./. When the last cutting into lengths is complete, the blank length set in the setter 30 changes from to L^ (as mentioned above, L^ has been preset) in response to the cutting complete signal for the last cutting into length . Now, the dividing unit 51 outputs = £/L2" In resPonse to the cutting complete signal, which is the external signal A, the ring counter 4 7 changes in its counts and gives a signal to select the pair of counter 48 and memory 49 corresponding to its new count. If the counter 4 8a and the memory 4 9a are selected, for example, the former starts the counting and the latter newly registers the coefficient from the dividing unit 51 . When the count- reaches the value X, the counter 4 8a gives a signal. In other words, the instant the last blank of length has left the sandwitch belt conveyor 4, the counter 4 8a gives- an output signal. The data selector 52 selects the memory 4 9a, which gives the coefficient • The rest is the same as when the blank length is fixed. The presser is controlled so that the brush presses the blank with the new length L^ at a correct timing when it 2 017 has just left the sandwitch belt conveyor.

The circuit arrangement is such that the result of computation M ~ ^b+ ^ from the counter 40 will be zero. If M is less than zero (<^0) , the error voltage Vc will be negative. Thus, the speed reference voltage Vo is V^ + (~|vc| ) =V^ - )vc| . This means that it is lower than the reference voltage V^ by the absolute value of the error voltage Vc. Therefore, the second motor 14 for the blank presser is decelerated so that the pulse signal <pQ will decrease. Thus, M(-K^A - <p^ + E) will go back to zero.

If M becomes above zero l~?0) , Vc will be positive. Thus, Vo (=VA +■ Vc) is higher than the reference voltage V^ by the error voltage Vc. The second motor 14 is accelerated so that the pulse signal p will increase. 1 B Thus, M will go back to zero. In short, control is made so that the value M will be zero. This means that the second motor 14 for the blank presser is controlled so as- to rotate at a predetermined ratio of revolutions with respect to the first motor 8 for the conveyor.

Summing up, what is done in this controi system is to multiply the pulse signal proportional to the blank feed speed by a coefficient K (= £/L) , use the signal as the reference speed .of the second motor 14 for the blank presser 9, compare the actual speed of the sandwitch belt conveyor 4 with the reference speed, and if there is 2013 17 any difference therebetween, accelerate or decelerate the second motor 14 to eliminate the difference. If there is any time difference between the occurrence of the detection signal S and that of the timing signal T (this means that the crank disc 13 is turning too quickly or too slowly for satisfactory pressing of the blank), too, the second motor 14 is accelerated or decelerated according to the amount of time difference. This compensation is performed by means of the position compensation circuit 35.

The sandwitch belt conveyor 4 may be replaced with any other type of conveyor, e.g. a suction conveyor.

Although in the preferred embodiment a brush is used for the blank presser, it may be replaced with a roller or any other suitable member.

Although in the preferred embodiment the brush is adapted to rock, it may be adapted for an up-and-down or any other movement.

The control system for a blank presser according to the present invention may be used with any other type of conveyor than the conveyor 5 used in this invention, e.g. a vertically movable stacker on which the blanks are stacked one upon another.

For the control system for the blank presser in accordance with the present invention, a computer such as a microcomputer may be used with the use of software (program) 2013 1 for part or all of the control.

It will be under-stood from the foregoing that the present invention eliminates the need for watching and manual adjustment of position or movement of the blank presser because the blank presser is automatically controlled according to the change in the blank length and the blank feed speed to ensure that the blanks will be timely held down by the brush so that they will not jam up.

Claims

WHAT WE CLAIM IS:

1. A control system for controlling a blank presser used to touch or hold down each of blanks fed one after another from a conveyor, comprising setting a value (L) proportional to the length of the blanks fed from said conveyor and a value (£) proportional to the distance by which said blank presser moves in one cycle of its operation, generating a signal ( <ftp) proportional to the speed at which said blanks are fed and a signal ( <pg) proportional to the speed of said blank presser, performing computation expressed by XjL x - tpB , combining an error voltage proportional to the result of computation with a reference voltage proportional to said signal ( <pA) multiplied by JJ./L, and controlling a drive for said blank presser by use of the combined voltage so that the blanks will be held down by said blank presser at a correct timing.

2. The control system as claimed in claim 1, wherein if there is any deviation in the position of said blank presser from its correct position, a compensation value (E) proportional to the amount of the deviation is added and computation expressed by JL/L x (p^ - + E is performed to obtain said error voltage. - 16 - ^ an 4L, <iJJ (j U 7

3. The control system as claimed in claim 1 or 2, wherein each time one blank leaves said conveyor, said computation is started on basis of the length of the blank next to the blank which has just left said conveyor.

4. A control system for controlling a blank pressure substantially as herein described with reference to the accompanying drawings. RENGO CO.LTD. By Their Attorneys HENRY HUGHES LIMITED By: